The wall surrounding the port keeps the "aliens" quarantined. The wall is more of a metaphorical barrier than anything else; however, even though it has a no-trespassing sign, it is low enough for someone to climb over.

2. Why do you think the citizens of Anarres do not climb the wall?

In the anarchist society of Anarres one of the things that keeps citizens from climbing the wall and entering the port is their fearful hatred of the Urrasti.

3. How does Shevek cope with leaving behind the familiarity of his world?

Shevek leaves behind the familiarity of his world for the strange world of the Urrasti, and it is a change that he compares to death. The narrator describes this shock as a strange crossing over "in that gap between the beginning of a step and its completion, and at the end of the step he stood on a new earth."